The present invention relates to a device for the thermal treatment of solid and sludge-like organic substances and of inorganic substances contaminated with organic substances. More particularly, the present invention relates to an upright cylindrical reactor which is filled with ceramic or metal balls and is provided with an agitator for moving the balls in a radial and an axial direction.
Reactors with fixed or movable ball charges and also multistage furnaces or disk dryers are known for the thermal treatment of organic and inorganic substances in upright cylindrical furnaces.
Thus, DE-OS 30 28 193 describes a device for the treatment of organic substances in which largely spherical ceramic structures are moved by an agitator in such a manner that they do not agglomerate, cake, or stick together due to the separated decomposition products. However, in furnaces of rather large diameter, only relatively small amounts of substances can be processed in that manner on the order of 1 kg/h since problems occur in the transmission of heat. In the case of a furnace having a diameter of more that 15 cm, the integral thermal conductivity of the filler charge is generally no longer sufficient to prevent undecomposed charge products from breaking through in the middle of the furnace.
DE-PS 6 46 182 teaches moving bituminous fuels in a heated, upright, cylindrical reactor in an axial direction in order to subject them to a low-temperature carbonization, whereby the fuels are transported upward via a worm in the center of the reactor from below and sink down from above on the wall of the reactor. However, this device is not suitable for the thermal decomposition and conversion of organic and inorganic substances since the filler bed can easily agglomerate.
DE-P 32 05 569 describes a device for the thermal decomposition and conversion of organic and inorganic substances which is composed of a heated, upright, cylindrical reactor with ceramic fillers and an agitator, consisting of agitator shaft, carrier arms and one or more helices.
Disadvantages of all these devices are the insufficient heat supply during indirect heating via the wall, a very high charge weight in the case of rather large bulk heights and a churning or mixing of the charge which is insufficient in the case of rather large charge heights, that is, in the case of an unfavorable ratio between charge height and reactor diameter.
Multistage furnaces are described in K. J. Thome-Kozmiensky, EF-Yerlag fuer Energie- und Umwelttechnik GmbH, [EF Publishing House for Energetic and Environmental Technology] Berlin 1985, pp. 381-391 which are also called disk furnaces or disk driers, depending on the area of application. The furnaces consist of a housing which exhibits an essentially cylindrical form and is arranged in a standing position with disks arranged in stages over each other in the interior. The material is moved over the disks by means of rabble or raking arms and with a centrally arranged, upright drive shaft. A direct drying process combined with a combustion process takes place in this furnace. The fuel, such as thick sludge, filter cake, filter briquette or waste sewage sludge mixture is placed on the uppermost hearth or disk. During the entire process, the material is turned by the agitator teeth of the rabble arms and transported further. As a result the material falls from level to level through shafts arranged in alternating fashion on the inside or the outside. The constant motion produces the exchange surface between the material and the air-gas current necessary for the reaction by spreading it out on the hearth surfaces.
Disadvantages in these devices are the large number of individual levels or stages and therewith the necessary great over-all height of the furnace in order to achieve the necessary minimum dwell time in the furnace for the substance to be treated as well as the non-defined movement of material on the individual levels, which results in agglomerations and therewith to a low material surface, which should be as large as possible in drying and combustion processes. In addition, an undesirable large dwell time spectrum of the substance to be treated results as a consequence of the disordered movement of charge material.